Behavioral and biochemical characteristics were investigated in neonatal brain dopamine depleted rats, a possible animal model of hyperactive (learning disability) children. On days 2 and 4 after birth, each rat of F344/Du strain received bilateral intraventricular injections of 6-hydroxydopamine (70mug). The results are as follows.1. Hyperactivity occurs prominently during the developing (premature) age. 2. Marked learning deficits appears on some (one-way and shuttle) types of avoidance tasks, which might be brought from prominent rearing and jumping responses under stressful situation. 3. Appetitive maze learning is also deteriorated. 4. Rewarding effects to dopaminergic stimulants are not changed. 5. Tissue contents of brain dopamine profoundly decrease, but extracellular concentration of dopamine remains to be relatively high. These results suggest that neonatal dopamine depleted rats are a promising animal model of hyperactive children.